1. Field of the Invention
This invention relates to a semiconductor device having a thin film resistor integrated therein and a method of producing the same as a molded resin package.
2. Description of the Related Art
Conventionally, a thin film resistor is formed and integrated with an insulating component of an IC, LSI or the like, to be used as a resistor.
This thin film resistor is usually composed of chromium (Cr) and silicon (Si) because the temperature coefficient of the resistance (TCR) thereof is low, and therefore any variations of the resistance due to changes in the temperature thereof are small.
Also, the TCR of this kind of thin film resistor composed of Cr and Si can be further lowered by varying the ratio of the content of Cr and Si.
Nevertheless, this kind of thin film resistor has a disadvantage in that it is difficult to make the TCR zero, and in general, preferably the value of .DELTA.R/R.sub.25, as shown in FIG. 7, is always zero even when the temperature is varied.
FIG. 7 shows the temperature dependency of the resistor value, and for the above purpose, a condition of a .alpha.=0 and .beta.=0 is required in the following equation obtained by the method of least squares. EQU .DELTA.R/R.sub.25 =.alpha.(T-25)+.beta.(T-25).sup.2
Wherein R.sub.25 represents a resistance value at a temperature of 25.degree. C., .DELTA.R represents a variation of the value (R.sub.T -R.sub.25) of the resistance measured at the temperature T and R.sub.25, .alpha. represents a primary coefficient, and .beta. represents a secondary coefficient.
As shown in FIG. 8, a problem arises in that the condition of .alpha.=0 can be realized but another condition, i.e., .beta.=0 cannot be simultaneously realized.
It is considered that the reason for the non-linearity of the graph shown in FIG. 7 is that, when the mobility .mu. becomes greater due to the existence of the microcrystal of the CrSi.sub.2 in the thin film resistor composed of a Cr--Si compound, the effect of the lattice vibration caused by the change in temperature becomes remarkable, and thus the resistance represented by the following equation will be varied because variation of the .mu. becomes large as the temperature is raised. ##EQU1##